A typical installation for a modern dome theater is shown in FIG. 1. Most modern dome theaters 1 utilize a dome 2 which is tilted forward and which has unidirectional seating 3 mounted on a stadium-type seating deck 4. An omni-type, large format film projector 5 is then situated within the theater space 6 which is defined by the dome 2. Examples of such dome theaters would include the IMAX™ Dome system, available from Imax Corporation, and the Cinedome™ format available from Iwerks.
The projector 5 is generally positioned behind the center 7 of the dome 2 or, as an alternative, at the center 7 of the dome 2, and typically uses a “fisheye” type lens (not shown) that has a very large field-of-view (e.g., 150 to 180 degrees). The projector 5 is accessed from a sub-floor 8 (i.e., from under the seating deck 4). A so-called “dog house” 9 is provided to contain the projector 5, which typically protrudes into the theater space 6. This leads to the disadvantage that valuable seating space is taken up in a prime viewing location, that being the center of the theater 1.
Another major problem with modern dome theaters is caused by scattered light. Since the projection screen (the dome 2) is curved, the image projected onto one portion of the screen can scatter light onto remaining portions of the screen. This leads to the disadvantage that the contrast of the resulting image can be reduced.
Another problem associated with modern dome theaters is the difficulty of obtaining sufficient image resolution, primarily due to the extremely wide field-of-view of the projection system. Eye-limited resolution over a hemispheric field-of-view requires a large number of pixels. This number is given by the following equation:       Number    ⁢                   ⁢    of    ⁢                   ⁢    pixels    =                              (                      2            ⁢                                                   ⁢            π            ⁢                                                   ⁢            steradians                    )                ⁢                              (                                          57.3                ∘                            ⁢                              /                            ⁢              steradian                        )                    2                ⁢                              (                          60              ⁢                                                           ⁢              arc              ⁢                                                           ⁢              min              ⁢                              /                            ⁢              deg                        )                    2                                      (                      0.5            ⁢                                                   ⁢            arc            ⁢                                                   ⁢            min            ⁢                          /                        ⁢            pixel                    )                2              =          300      ⁢                           ⁢      million      ⁢                           ⁢      pixels      No medium is presently known which is capable of achieving this resolution. For example, large-format films (15 perf/70 mm) are capable of an effective pixel resolution on the order of 10 to 12 million. Video projectors, however, are currently only capable of an effective pixel resolution on the order of 3 million.
The limited resolution of video projectors has prevented the use of “single-lens” projection schemes. Instead, multiple, edge-blended projectors have been required to achieve a large, seamless, high-resolution image. Such systems, however, have the disadvantages of being expensive and difficult to maintain. It is also difficult to format content for such systems because the images must be split into separate frames, for projection by individual projectors, which must carefully reconstruct the image on the dome screen using edge-blending techniques.
Another problem associated with modern dome projection systems is that the brightness of the image tends to be somewhat limited. While flat-screen theaters easily fulfill the current SMPTE cinematic standard for brightness of 12 foot-Lamberts, dome theaters usually provide a brightness on the order of 3 to 4 foot-Lamberts, or less, due to their large image area and the limited brightness of the projectors.